The present invention relates generally to pain controlling compositions and more particularly to a pain controlling composition containing butyl aminobenzoate.
Shulman U.S. Pat. No. 4,599,354 discloses a pain controlling composition consisting essentially of a sterile, stable suspension of butyl aminobenzoate in a non-toxic, aqueous carrying medium in which the butyl aminobenzoate is insoluble; and the disclosure thereof is incorporated herein by reference.
The butyl aminobenzoate constitutes about 5-15 wt. % of the composition, and the aqueous carrying medium consists essentially of water as the major constituent and up to about 10 wt. % polyethylene glycol as a suspending agent for the butyl aminobenzoate.
The composition is typically administered by injection to a body region where pain control is desired, and it is important that the butyl aminobenzoate be uniformly distributed, as a physical suspension, throughout the aqueous carrying medium at the time the composition is administered.
Difficulties have been encountered in obtaining the desired physical suspension or, once obtained, in maintaining it. In some instances when polyethylene glycol has been used as the suspending agent, there was floatation by the butyl aminobenzoate. Attempts to employ polysorbate 80, a wetting agent, to suspend the butyl aminobenzoate have resulted in settling by the butyl aminobenzoate.